Proteotoxic stress plays an important role in the pathogenesis of Huntington's disease (HD). Autophagy is proposed as a compensatory mechanism to remove protein aggregates under proteotoxic stress by up-regulating p62 expression. In the present study, we investigated the molecular action of p62 to proteotoxic stress in HD cells. Using two different HD cellular models, STHdhQ7 and STHdhQ111 cells derived from wild type and HD knock-in mice and human fibroblasts from healthy and HD patients, we found that HD cells are more vulnerable to cell death under proteotoxic stress and during stress recovery. We further showed that P62 was up-regulated in both STHdhQ7 and STHdhQ111 cells in response to the stress with distinct subcellular localization patterns. While dispersed p62 puncti were found in STHdhQ7 cells, p62 bodies were initially present in the lysosomes and accumulated to the juxtanuclear regions of STHdhQ111 cells as MG132 incubation continued. Unlike in STHdhQ7 cells, p62 puncti were not associated with K48-linked polyubiquitinated protein aggregates or proteasomal components in STHdhQ111. Interestingly, addition of cysteine during MG132 incubation rescued cell death in STHdhQ111 cells caused by stress recovery and altered the subcellular distribution of p62. Our data suggest that aberrant positioning of p62 affects the proteasomal clearance of protein aggregates and may contribute to the increased vulnerability to proteotoxic stress-induced cell death in HD cells.

No abstract

Background Ischemic cerebrovascular disease leads to the activation and differentiation of neural stem cells (NSCs) into mature neurons and glia cells to repair nerve damage. Astragalus flavone (ASF) has shown its potential role in proliferation and differentiation into dopamine neurons of NSCs. Material/Methods Cerebral infarction models were constructed to determine the effects of ASF on NSCs in vivo and in vitro. Results ASF therapy had the ability to reduce the neurologic function scores and the cerebral infarction volume of the cerebral infarction model. Moreover, ASF was able to increase BrdU-positive cells and promote the expression of Nestin, β-Tubulin III, and O4, while decreasing the expression of GFAP. qRT-PCR and western blot assays showed ASF promoted the expression of Mash1, Math1, and Ngn2 mRNA and protein in cerebral infarction rats. Meanwhile, ASF (20 μg/ml) was able to increase EdU-positive cells and promote the expression of Nestin, β-Tubulin III, and O4 of NSCs at day14 in vitro. In normoxia, ASF obviously promoted the expression of Mash1, Ngn1, and Ngn2 mRNA and proteins, but in hypoxia, ASF promoted the expression of Notch1 and Math1 mRNA and proteins and inhibited the expression of Ngn1 and Ngn2 mRNA and proteins. Conclusions ASF therapy can improve the neurologic functions and reduce the cerebral infarction volume in a cerebral infarction model. Moreover, ASF promoted the proliferation of NSCs and induced differentiation into neurons and oligodendrocytes, which might be involved in regulating factors in Notch signaling.

No abstract